Breathing Moonrocks

May
5, 2006: An early, persistent problem noted by Apollo
astronauts on the Moon was dust. It got everywhere, including
into their lungs. Oddly enough, that may be where future Moon
explorers get their next breath of air: The moon's dusty layer
of soil is nearly half oxygen.

"All
you have to do is vaporize the stuff," says Eric Cardiff
of NASA's Goddard Space Flight Center. He leads one of several
teams developing ways to provide astronauts oxygen they'll
need on the Moon and Mars. (See the Vision
for Space Exploration.)

Lunar
soil is rich in oxides. The most common is silicon dioxide
(SiO2), "like beach sand," says Cardiff.
Also plentiful are oxides of calcium (CaO), iron (FeO) and
magnesium (MgO). Add up all the O's: 43% of the mass of lunar
soil is oxygen.

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Cardiff
is working on a technique that heats lunar soils until they
release oxygen. "It's a simple aspect of chemistry,"
he explains. "Any material crumbles into atoms if made
hot enough." The technique is called vacuum pyrolysis--pyro
means "fire", lysis means "to separate."

"A
number of factors make pyrolysis more attractive than other
techniques," Cardiff explains. "It requires no raw
materials to be brought from Earth, and you don't have to
prospect for a particular mineral." Simply scoop up what's
on the ground and apply the heat.

In
a proof of principle, Cardiff and his team used a lens to
focus sunlight into a tiny vacuum chamber and heated 10 grams
of simulated lunar soil to about 2,500 degrees C. Test samples
included ilmenite and Minnesota Lunar Simulant, or MLS-1a.
Ilmenite is an iron/titanium ore that Earth and the Moon have
in common. MLS-1a is made from billion-year-old basalt found
on the north shore of Lake Superior and mixed with glass particles
that simulate the composition of the lunar soil. Actual lunar
soil is too highly prized for such research now.

In
their tests, "as much as 20 percent of the simulated
soil was converted to free oxygen," Cardiff estimates.

What's
leftover is "slag," a low-oxygen, highly metallic,
often glassy material. Cardiff is working with colleagues
at NASA's Langley Research Center to figure out how to shape
slag into useful products like radiation shielding, bricks,
spare parts, or even pavement.

The
next step: increase efficiency. "In May, we're going
to run tests at lower temperatures, with harder vacuums."
In a hard vacuum, he explains, oxygen can be extracted with
less power. Cardiff's
first test was at 1/1,000 Torr. That is 760,000 times thinner
than sea level pressure on Earth (760 Torr). At 1 millionth
of a Torr -- another thousand times thinner -- "the temperatures
required are significantly reduced."

Cardiff
is not alone in this quest. A team led by Mark Berggren of
Pioneer Astronautics in Lakewood, CO, is working on a system
that harvests oxygen by exposing lunar soil to carbon monoxide.
In one demonstration they extracted 15 kg of oxygen from 100
kg of lunar simulant--an efficiency comparable to Cardiff's
pyrolysis technique: more.

D.L.
Grimmett of Pratt & Whitney Rocketdyne in Canoga Park,
CA, is working on magma electrolysis. He melts MLS-1 at about
1,400 deg. C, so it is like magma from a volcano, and uses
an electric current to free the oxygen: more.

Finally,
NASA and the Florida Space Research Institute, through NASA's
Centennial Challenge, are sponsoring MoonROx, the Moon Regolith
Oxygen competition. A $250,000 prize goes to the team that
can extract 5 kg of breathable oxygen from JSC-1 lunar simulant
in just 8 hours.

The
competition closes June 1, 2008, but the challenge of living
on other planets will last for generations.